The invention relates to a logic input device of an electronic equipment for an industrial automatic control system comprising a first detection stage having a plurality of input circuits and an acquisition circuit for acquisition of the input signals detected by said input circuits.
The logic input function implemented in electronic equipment for automatic control systems of on-board installations, in particular of rail transport vehicles, generally requires a large current in the logic inputs. The problem arising in conventional equipment is then that of heat dissipation in the measuring resistors, for a logic input at a voltage of 110 Volts for example, and with a current intensity of 10 mA, will dissipate a thermal power of 1.1 W. The global heat dissipation is naturally proportional to the number of logic inputs and often requires the use of cooling devices by heat sink or heat pipes to dissipate the heat to the outside. The electrical power supply of the equipment being performed from a safety power system with a backup battery bank, this results in addition in a loss of electrical power of the vehicle.
The object of the invention is to achieve a logic input device with reduced heating and with electrical energy recovery.
The logic input device according to the invention is characterized in that
each input circuit of the first detection stage comprises a first transformer having a primary winding connected to the corresponding input by means of a first chopping transistor, and a secondary coil connected to the diode rectifier circuit,
a first clock is designed to send control signals to the first chopping transistor,
adjustment means co-operate with the first clock for adjusting the frequency of the control signals or of the duty cycle for voltage adaptating of said input circuit,
a logic level detector is inserted in the secondary or primary circuit of the first transformer and is electrically connected to the acquisition circuit,
and a second recovery stage is connected to a battery supplying power to the equipment to restore the energy drained by the set of input circuits of the first detection stage.
The heat dissipation is thus reduced enabling the use of heat sinks to be avoided, resulting in addition in a saving of electrical energy due to the effect of energy restoration to the battery.
According to one feature of the invention, the logic level detector is formed by a resistor of a measuring shunt or by an opto-coupling element having a receiver delivering the input signal to the acquisition circuit.
According to one embodiment, the second energy recovery stage comprises a second voltage step-up transformer equipped with a primary winding electrically connected to the diode rectifier circuit of the first transformer, and with a secondary winding connected to the battery by means of a rectifying and filtering circuit with a diode and capacitor. A filtering capacitor is associated to the diode rectifier circuit of each input circuit, the filtering capacitor being inserted in the secondary circuit after the logic level detector.
The primary winding of the second transformer is electrically connected in series with a second chopping transistor controlled by a second clock. The second clock is in phase opposition with the first clock.
According to another feature of the invention, a voltage sensor is associated to the input of the second recovery stage and co-operates with a regulating circuit of the second clock to adjust the frequency of the chopping signals applied to the second transistor.
The second chopping transistor can be eliminated in the primary circuit of the second transformer if the voltage rectified by the input circuits is not filtered.
According to another embodiment, the second energy recovery stage is connected directly to the diode rectifier circuit of each input circuit of the first detection stage. A free-wheel diode is connected to the input of a filtering circuit and is moreover connected in parallel to the terminals of the secondary winding and of the rectifier diode.